1. Field of the Disclosure
The present invention relates in general to storage media and, in particular, to a method for lubed tape burnish for producing thin lube media.
2. Description of the Related Art
Hard disk drives read from and write to magnetic patterns on magnetic media. Hard disk drives have been used for over forty years to store digital data, and offer low cost, high recording capacity, and relatively rapid data retrieval. While the basic principle of reading and writing magnetic patterns on rotating disks remains the same, components of the disk drive, particularly the read-write head and the disks have significantly evolved.
Thin films of magnetic metal are typically sputtered on a platter to form a magnetic media disk. Thin films allow more narrow magnetic cells, which represent a data bit, to be formed. The narrower magnetic cell results in higher recording and storage densities. Additionally, metallic thin films with limited surface roughness may be formed on a very smooth platter. Smooth films allow the head to “fly” closer to the magnetic cells, yielding higher read-back amplitudes.
Surface roughness limits how low a head can approach the media, and adds to the overall contribution of noise from the magnetic layer of magnetic media disks. Advancements in the design of recording heads, particularly the introduction of magneto-resistive heads, also call for continuing reductions in surface roughness.
Pad burnish is an important process in manufacturing magnetic recording media following sputter deposition of magnetic layers, deposition of an overcoat and lubricant dipping. The purpose of pad burnish is to polish off high asperities on the disk surface and thus to increase glide yield. However, poor burnish often damages the disk by causing overcoat scratches and producing solid particles, which leads to poor corrosion resistance and low glide yield. It has been known that a minimum amount of mobile (unbonded) lubricant is required to minimize damage to the disk, exemplified by the glide yield versus time delay of sputter-to-lube or lube-to-burnish. Longer sputter-to-lube delay decreases the initial bonded fraction of lubricant (due to contamination of water and organics), whereas longer lube-to-burnish delay increases the bonded fraction (governed by lubricant bonding kinetics). Therefore, longer sputter-to-lube delay and shorter lube-to-burnish delay produce high glide yield.
However, too much free lubricant causes severe flyability problems, such as lube pick-ups, moguls and depletion, and also reduces magnetic clearance. The total lubricant thickness is limited in order to reduce magnetic spacing and achieve high areal density.
One conventional solution discloses a mixture of both low and high molecular weight lubricants applied to media. See, e.g., U.S. App. Pub. 2007/0248749, to Guo et al, which is incorporated herein by reference. This design reduces burnish damage and increases glide yield without compromising disk flyability, durability and general quality. However, this method also includes a fixed time delay for lube-to-burnish, which can affect manufacturing considerations. Thus, improvements in lubrication design and implementation continue to be of interest.